In recent years, in radio communications—and in mobile communications in particular—various kinds of information such as images and data have become objects of transmission in addition to voice. With demand for the transmission of various kinds of content expected to grow steadily in the future, an increased need for high-speed transmission is also anticipated. However, when high-speed transmission is carried out in mobile communications, the effect of delayed waves due to multipath propagation cannot be ignored, and transmission characteristics degrade due to frequency selective fading.
Multicarrier (MC) communication methods such as OFDM (Orthogonal Frequency Division Multiplexing) are now attracting attention as one kind of technology for combating frequency selective fading. Multicarrier communication is a technology that achieves high-speed transmission by transmitting data using a plurality of carriers (subcarriers) whose transmission speed is suppressed to a level at which frequency selective fading does not occur. With the OFDM modulation method, in particular, the subcarriers on which data is placed are mutually orthogonal, making this the multicarrier modulation method offering the highest spectral efficiency. Moreover, the OFDM modulation method can be implemented with a comparatively simple hardware configuration. For these reasons, OFDM is an object of particular attention, and various related studies are being undertaken.
One example of such studies is a technology that increases system throughput by executing control so that transmission of a subcarrier with poor channel quality is not performed (see Non-patent Document 1, for example).
Non-patent Document 1: Noriyuki MAEDA, Seiichi SAMPEI, Norihiko MORINAGA, “Performance of the Delay Profile Information Channel based Subcarrier Transmit Power Control Technique for OFDM/FDD Systems” IEICE Transactions, B, Vol. J84-B, No. 2, pp. 205-213 (February 2001)